Night vision systems generally comprise a number of components. A front collection lens system collects light, such as infrared light, from the environment and relays the light to a night vision tube. The collection lens system also typically provides for focus adjustment. The tube magnifies the number of received photons. In a typical tube, incoming light strikes a photocathode plate causing the emission of electrons through a microchannel plate. The electrons then form an image on a photocathode. At the proximal end, an eye piece then conditions the image for the viewer and typically provides diopter adjustment. The tube is usually contained within a housing that is threaded at either end to mate with the front collection lens system and the eye piece lens system.
In general, it is not uncommon for the night vision systems to be disassembled and/or repaired and/or upgraded. For example, the collection lens system or the eyepiece lens system could become damaged through impact. Moreover, this disassembly and/or repair and/or upgrade can occur in the field and/or by untrained personnel. On the other hand, the same night vision systems must be mechanically robust such that they remain operational in harsh environments including combat conditions.